The Internet Protocol multimedia subsystem (Internet Protocol Media Subsystem, IMS) is an IP-based access-independent network architecture. It is a convergent core network that can be shared by a mobile network and a fixed network. the IMS network is capable of providing convergent services for users that use different access manners such as 2.5G, 3G, WLAN (wireless local area network), and fixed broadband, and is considered as a basis of the next-generation network in the field.
To access the IMS core network, a terminal needs to traverse a private network (for example, an enterprise network accessed by the terminal). Specifically, a private network IP address is used within the enterprise network, and a network address translation (NAT) device is deployed at the edge of the enterprise network. Therefore, the terminal needs to traverse the NAT device and access a server of the IMS core network; or if an application layer proxy server is deployed at the edge of the enterprise network, the terminal needs to traverse the application layer proxy server and access the server of the IMS core network.
The prior art provides a method for traversing a private network. Specifically, an Internet Protocol Security virtual private network (Internet Protocol Security VPN, IPSec VPN) gateway is deployed in each of an enterprise network and an IMS network, so as to set up an IPSec VPN tunnel between the enterprise network and the IMS network by using the deployed IPSec VPN gateways; and routes of terminals in the enterprise network converge to the IPSec VPN gateway in the enterprise network, and the IPSec VPN gateway in the enterprise network performs operations such as encapsulation/decapsulation on service data. Specifically, when a terminal sends service data to the IMS core network, a route of the service data sent by the terminal is modified, and the service data is routed to the IPSec VPN gateway in the enterprise network first. The IPSec VPN gateway encapsulates the service data, and then transmits the service data over the IPSec VPN tunnel to the IPSec VPN gateway in the IMS core network. The IPSec VPN gateway in the core network decapsulates the service data, and sends it to the server in the IMS core network.
In the prior art, the IPSec VPN gateway needs to be deployed in the enterprise network, the data route of the terminal needs to be modified, and great modification of the enterprise network is required.